speed and crusing
 

I got a problem maybe lol
99 silverado 5.3 z71
After getting up to speed my truck seems to lose speed fast
I am not sure what od is obd seems 10+ mph off
I got power no muffler no sure on grease on hubs or if tranny
If i can find a police sign with radar i can get speed
And no not doing a dyno

Not sure what the question is. If your trying to check to see if your speedometer is reading correctly, get a gps(Tom Tom/Garmen, ect.) and check it against that. Don't have one, odds are you know someone that does. Ask to borrow for and hour, plug it in and go for a ride. Loosing speed quickly after letting off the gas? Check for sticking caliper. What kind of tires do you have? Oversize? Bigger tires mean more rolling resistance. Lift kit? Grease every zert on the undercarriage and make sure your tires are inflated properly and then give more readable info on the truck so maybe we can be of more help to you.

Sorry was late and i know it was too much data lol
So after getting up to speed (60) (70) and let off gas truck slows down really fast like trans is i will look rotors tomorrow
Tires are stock i think
Z71 235-75/r16 i think

What are the engine rpm's before you let off at 65-70 mph? Maybe your trans is not shifting into 4th gear. RPM's would let you know if your in the right gear at those speeds.

Idk 4k~5k

If it is 4-5000 then I would say you are still in 3rd gear.

Dont feel like trany not sifting ill see what rpm are at and let u know
Feels like tires/hubs/brakes idk